Method for reducing dimensions between patterns on a photoresist

ABSTRACT

A semiconductor manufacturing method that includes defining a substrate, depositing a polysilicon layer over the substrate, depositing a layer of photoresist over the polysilicon layer, patterning and defining the photoresist layer, depositing a layer of inorganic material over the patterned and defined photoresist layer, wherein the layer of inorganic material is conformal and photo-insensitive, and anisotropic etching the layer of inorganic material and the layer of semiconductor material.

DESCRIPTION OF THE INVENTION

1. Field of the Invention

This invention relates in general to a semiconductor manufacturingprocess and, more particularly, to a photolithographic method havingreduced dimensions between patterns on a photoresist.

2. Background of the Invention

With sub-micron semiconductor manufacturing process being the prevalenttechnology, the demand for a high-resolution photolithographic processhas increased. The resolution of a conventional photolithographic methodis primarily dependent upon the wavelength of a light source, whichdictates that there be a certain fixed distance between patterns on aphotoresist. Distance separating patterns smaller than the wavelength ofthe light source could not be accurately patterned and defined.

Prior art light sources with lower wavelengths are normally used in ahigh-resolution photolithographic process. In addition, the depth offocus of a high-resolution photolithographic process is shallowercompared to a relative low-resolution photolithographic process. As aresult, a photoresist layer having a lower thickness is required forconventional photolithographic methods. However, a photoresist layerhaving a lower thickness is susceptible to the subsequent etching stepsin a semiconductor manufacturing process. This relative ineffectiveresistance to etching reduces the precision of patterning and definingof a photoresist. These limitations prevent the dimensions of patternson a photoresist from being reduced.

It is accordingly a primary object of the invention to provide a methodfor reducing the distance separating patterns on a photoresist layer. Inaddition, it is another object of the invention to provide a method toenhance the etching resistance of a patterned photoresist layer.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a semiconductormanufacturing method that includes depositing a layer of semiconductormaterial over a substrate, providing a layer of photoresist over thelayer of semiconductor material, patterning and defining the photoresistlayer, depositing a layer of inorganic material over the patterned anddefined photoresist layer, wherein the layer of inorganic material isphoto-insensitive, anisotropic etching the layer of inorganic materialand the layer of semiconductor material, and removing the patterned anddefined photoresist layer.

In another aspect, the layer of inorganic material is substantiallyconformal.

In yet another aspect, the step of depositing a layer of inorganicmaterial is performed at a temperature lower than a stabilitytemperature of the patterned and defined photoresist layer.

Also in accordance with the present invention, there is provided asemiconductor manufacturing method that includes defining a substrate,depositing a layer of semiconductor material over the substrate,providing a layer of photoresist over the layer of semiconductormaterial, patterning and defining the photoresist layer to form at leastone photoresist structure having at least one substantially verticalsidewall and one substantially horizontal top, depositing aphoto-insensitive material over the at least one photoresist structureand the layer of semiconductor material, wherein an amount of thephoto-insensitive material deposited on the top of the photoresiststructure is substantially greater than an amount of thephoto-insensitive material deposited on the at least one sidewall of thephotoresist structure, etching the photo-insensitive material and thelayer of semiconductor material, and removing the at least onephotoresist structure.

In one aspect, the amount of the photo-insensitive material deposited onthe top of the photoresist structure is substantially greater than anamount of the photo-insensitive material deposited on the layer ofsemiconductor material.

Further in accordance with the present invention, there is provided asemiconductor manufacturing method that includes defining a substrate,providing a first layer over the substrate, providing a layer ofphotoresist over the first layer, patterning and defining thephotoresist layer to form at least two photoresist structures, whereineach of the photoresist structures includes substantially verticalsidewalls and a substantially horizontal top, and wherein thephotoresist structures are separated by a space, depositing a layer ofpolymer on the tops of the photoresist structures and the spaceseparating the photoresist structures, wherein an amount of the polymerdeposited on the tops of the photoresist structures is substantiallygreater than an amount of the polymer deposited on the sidewalls of thephotoresist structures, and etching the polymer layer on the tops of thephotoresist structures and the space between the photoresist structures,and the first layer.

In one aspect, the first layer is a dielectric layer.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are cross-sectional views of the semiconductor manufacturingprocess steps of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIGS. 1-3 are cross-sectional views of the semiconductor manufacturingprocess steps of the present invention. Referring to FIG. 1, the methodof the present invention begins by defining a wafer substrate 100. Thewafer substrate 100 may be of any known semiconductor substratematerial, such as silicon. A first layer 110 is then provided over thewafer substrate 100. In one embodiment, the first layer 110 is asemiconductor material, such as polysilicon. The first layer 110 mayalso be a dielectric layer or a metal layer. The first layer 110 may bedeposited over the wafer substrate 100 by any known deposition process.In another embodiment, the first layer 110 is a dielectric material, inwhich case the first layer 110 may be deposited or grown over the wafersubstrate 100.

An anti-reflection coating (ARC) layer 120 may optionally be providedover the first layer 110 to decrease the reflection from the first layer110 in the subsequent manufacturing steps. A photoresist layer 130 isthen provided over the ARC layer 120. In an embodiment in which an ARClayer is not provided, the photoresist layer 130 is deposited over thefirst layer 110. The photoresist layer 130 is then patterned and definedusing a known photolithographic process to form a patterned and definedphotoresist layer having a plurality of photoresist structures 130. Thephotoresist structures 130 include substantially vertical sidewalls 132and substantially horizontal tops 134. When the first layer 110 is asemiconductor material, the photoresist structures 130 functions to formconductors from the first layer 110.

Referring to FIG. 2, a second layer 150 is deposited over the patternedand defined photoresist layer 130 by a known chemical vapor depositionapparatus 140. Known chemical vapor deposition processes include plasmaenhanced chemical vapor deposition (PECVD) and low pressure chemicalvapor deposition (LPCVD). The second layer 150 may be organic orinorganic, and is photo-insensitive. In one embodiment, the second layer150 is a polymer layer. In another embodiment, the second layer 150 issubstantially conformal, covering both the tops 134 and sidewalls 132 ofthe photoresist structures 130. In one embodiment, the amount of thesecond layer 150 deposited on the tops 134 of the photoresist structures130 is substantially greater than the amount adhered to the sidewalls132. Having a substantially more of the second layer 150 deposited onthe tops 134, the photoresist structures 130 become more resistive tothe subsequent etching steps, thereby preserving the precision of thephotolithographic process. In addition, the step of depositing thesecond layer 150 is performed at a temperature lower than the stabilitytemperature of the photoresist structures 130. In other words, thesecond layer 150 is deposited at a temperature not affecting thestructural stability of the photoresist structures 130.

After the deposition of the second layer 150, the space between thephotoresist structures 130 is decreased, for example, from 0.22 micronsto 0.02 microns.

In the PECVD process, the pressure used is in the range of approximately10 mtorr to 20 mTorr. The power ranges from approximately 500 watts to800 watts. The deposition rate is between approximately 3,000 Å perminute and 6,000 Å per minute. In addition, the polymer layer 150comprises at least one hydrocarbon partially substituted by fluorine,the source for forming polymers. The partially-substituted hydrocarbonsmay be chosen from difluoromethane (CH₂F₂), a mixture of difluoromethaneand octafluorobutene (C₄F₈), and a mixture of difluoromethane andtrifluoromethane (CHF₃). In one embodiment, when thepartially-substituted hydrocarbons include CH₂F₂ only, the thickness “a”of a portion of the polymer layer 150 is the same as the thickness “b”of another portion of the polymer layer 150. In another embodiment, whena mixture of CH₂F₂ and C₄F₈ or a mixture of CH₂F₂ and CHF₃ is used, thethickness “a” is larger than the thickness “b.”Therefore, thethicknesses “a” and “b” may be varied by adjusting the ratios of CH₂F₂to C₄F₈ or those of CH₂F₂ to CHF₃.

Moreover, argon (Ar) and carbon monoxide (CO) may be mixed with thegases introduced during the PECVD process. Argon acts as a carrier toenhance etch uniformity of the photoresist layer 130 and the ARC layer120. The function of carbon monoxide is to capture fluorine radicals andfluoride ions generated by the fluoro-substituted hydrocarbons. As such,etching of the polymers during the deposition process is prevented,thereby enhancing the deposition rate of the polymer layer 150. Oxygen(O₂) and nitrogen (N₂) gases also can be added to the PECVD process.Contrary to the function of the carbon monoxide, the presence of oxygenserves to etch the polymer layer 150. Therefore, the deposition rate ofpolymer layer 150 can be controlled. Also, perfluorohydrocarbons, suchas hexafluoroethane (C₂F₆) and tetrafluoromethane (CF₄), can be mixedwith the gases combined with the plasma during the deposition becausethese gases, similar to the oxygen gas, etch the polymer layer 150.

Referring to FIGS. 3A and 3B, the second layer 150, the photoresiststructures 130, the ARC layer 120, and the first layer 110 are etchedanisotropically with a plasma-based dry etching process. The dry etchingprocess uses plasma 160 In an embodiment in which “a” is thicker than“b,” the thickness of the second layer 150 changes from “a” to “a−b”after the second layer 150 deposited over the ARC layer 120 iscompletely etched away. This shows that the second layer 150 providesexcellent resistance to the plasma etch process and therefore enhancesthe etching resistance of the photoresist structures 130.

As shown in FIG. 3B, when the anisotropic dry etching process continues,the second layer 150 acts as an etch stop and remains on the sidewallsof the photoresist structures 130. Thus, the dimensions between thepatterned photoresist and the underlying patterned first layer 110 arereduced. The photoresist structures 130 may be removed using anyconventional process.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A semiconductor manufacturing method, comprising:depositing a layer of semiconductor material over a semiconductorsubstrate; providing a layer of photoresist over the layer ofsemiconductor material; patterning and defining the photoresist layer;depositing a layer of inorganic material over the patterned and definedphotoresist layer, wherein the layer of inorganic material isphoto-insensitive; anisotropic etching the layer of inorganic materialand the layer of semiconductor material; and removing the patterned anddefined photoresist layer.
 2. The method as claimed in claim 1, furthercomprising a step of depositing a layer of polymer.
 3. The method asclaimed in claim 1, wherein the layer of inorganic material issubstantially conformal.
 4. The method as claimed in claim 1, whereinthe step of depositing a layer of inorganic material is performed at atemperature lower than a stability temperature of the patterned anddefined photoresist layer.
 5. The method as claimed in claim 1, whereinthe layer of inorganic material is deposited with plasma enhancedchemical vapor deposition at a pressure of between approximately 10mTorr to 20 mTorr.
 6. The method as claimed in claim 1, wherein thelayer of inorganic material is deposited with plasma enhanced chemicalvapor deposition at a rate of between approximately 3000 Å per minuteand 6000 Å per minute.
 7. The method as claimed in claim 1 furthercomprising a step of depositing an anti-reflection coating over thelayer of semiconductor material.
 8. The method as claimed in claim 1,wherein the layer of semiconductor material comprises one ofpolysilicon, dielectric material or metallic material.
 9. Asemiconductor manufacturing method, comprising: Defining a substrate;Depositing a layer of semiconductor material over the substrate;Providing a layer of photoresist over the layer of semiconductormaterial; Patterning and defining the photoresist layer to form at leastone photoresist structure having at least one substantially verticalsidewall and one substantially horizontal top; Depositing aphoto-insensitive material wherein the photo-insensitive material isinorganic over the at least one photoresist structure and the layer ofsemiconductor material, wherein an amount of the photoinsenstivematerial deposited on the top of the photoresist structure issubstantially greater than an amount of the photo-insensitive materialdeposited on the at least one sidewall of the photoresist structure;Etching the photo-insensitive material and the layer of semiconductormaterial; and Removing the at least one photoresist structure.
 10. Themethod as claimed in claim 9, wherein the step of depositing aphoto-insensitive material comprises a step of depositing a layer ofpolymer.
 11. The method as claimed in claim 9, wherein the step ofdepositing a photo-insensitive material is provided at a temperature notaffecting a stability of the at lest one photoresist structure.
 12. Themethod as claimed in claim 9, wherein the amount of thephoto-insensitive material deposited on the top of the photoresiststructure is substantially greater than an amount of thephoto-insensitive material deposited on the layer of semiconductormaterial.
 13. The method as claimed in claim 9, wherein the layer ofsemiconductor material comprises polysilicon.
 14. A semiconductormanufacturing method, comprising: defining a substrate; providing afirst layer over the substrate; providing a layer of photoresist overthe first layer; patterning and defining the photoresist layer to format least two photoresist structures, wherein each of the photoresiststructures includes substantially vertical sidewalls and a substantiallyhorizontal top, and wherein the photoresist structures are separated bya first space; depositing a photo-insensitive layer on the sidewalls ofthe photoresist structures such that the photoresist structures with thephoto-insensitive layer on the sidewalls thereof are separated by asecond space, wherein the first space is greater than the second space;and anisotropic etching of the photo-insensitive layer.
 15. The methodas claimed in claim 14, wherein the anisotropic etching step comprisesetching the first layer using the photoresist structures and thephoto-insensitive layer on the sidewalls of the photoresist structuresas a mask to form at least two first layer structures separated by athird space, and wherein the third space is narrower than the firstspace.
 16. The method as claimed in claim 14, wherein the first layercomprises one of polysilicon, dielectric material or metallic material.17. The method as claimed in claim 14, further comprising a step ofdepositing an anti-reflection coating over the first layer.
 18. Themethod as claimed in claim 14, wherein the photo-insensitive layercomprises polymer.
 19. The method as claimed in claim 14, wherein thestep of depositing a photo-insensitive layer is performed with plasmaenhanced chemical vapor deposition at a rate between approximately 3000Å per minute and 6000 Å per minute.
 20. The method as claimed in claim14, wherein the step of depositing a photo-insensitive layer isperformed at a temperature lower than a stability temperature of thepatterned and defined photoresist layer.
 21. A semiconductormanufacturing method, comprising: defining a substrate; depositing alayer of semiconductor material over the substrate; providing a layer ofphotoresist over the layer of semiconductor material; patterning anddefining the photoresist layer to form at least two photoresiststructures, wherein each photoresist structure includes at least onesubstantially vertical sidewall and one substantially horizontal top,and wherein the photoresist structures are separated by a first space;depositing a photo-insensitive material over the at least twophotoresist structures and the layer of semiconductor material, whereinan amount of the photo-insensitive material deposited on the top of thephotoresist structures is substantially greater than an amount of thephoto-insensitive material deposited on the at least one sidewall of thephotoresist structures, wherein the photoresist structures with thephoto-insensitive layer on the sidewalls thereof are separated by asecond space, and wherein the first space is greater than the secondspace; etching the photo-insensitive material and the layer of thesemiconductor material; and removing the at least one photoresiststructure.